In U.S. patent application Ser. No. 767,889 filed Aug. 21, 1985, a door frame is secured to an existing wood door frame of a house or building. The door frame is then used as part of a locking system for a security door that is hingedly mounted on the door frame. The door frame is made of tubular metal with the threshold member being secured to the bottoms of the side members of the door frame. This creates a problem when the threshold of the existing door frame is not true or level, which is generally the case, because the treshold member of the door frame to be mounted onto the existing door frame will not be in alignment with the existing threshold. The non-aligned threshold and threshold member will be difficult to seal and will create misalignment between the threshold and threshold member.